In a mobile cellular communications system, various communications nodes such as a base station and user equipment (User Equipment, UE for short) all have a capability of receiving and transmitting a signal. To avoid self-interference caused by a transmit signal to a receive signal in a same transceiver, communication is performed by using time division duplex (Time Division Duplex, TDD for short) or frequency division duplex (Frequency Division Duplex, FDD for short) in the prior art. However, spectrum utilization of FDD and spectrum utilization of TDD are relatively low. In a wireless full-duplex technology, receiving and transmitting may be simultaneously performed on a same radio channel, thereby improving spectrum utilization. However, in the wireless full-duplex technology, self-interference caused by a transmit signal to a receive signal in a same transceiver needs to be reduced as much as possible.
In the existing wireless full-duplex technology, a transmit/receive shared antenna may be used to transmit a signal and receive a signal. FIG. 1 is a block diagram of radio frequency self-interference processing for a transmit/receive shared antenna in the prior art. As shown in FIG. 1, a transmit/receive isolation component such as a circulator may be used to isolate a transmit channel and a receive channel. After passing through a power amplifier (Power Amplifier, PA for short), a transmit signal is input from a left side of the circulator, and is output from an upper side of the circulator to a shared antenna, so that the transmit signal is transmitted. A receive signal that is received from the shared antenna is input from an upper side of the circulator, is output from a right side of the circulator, and enters a low noise amplifier (Low Noise Amplifier, LNA for short) on the receive channel. To cancel a self-interference caused by the transmit signal to the receive signal, a signal may be split from the transmit signal by using a coupler or a power splitter disposed on the transmit channel, a self-interference signal is generated after the signal sequentially passes through an attenuator and a phaser, and then the self-interference signal is coupled with the receive signal by using a coupler or a combiner disposed on the receive channel, so as to cancel self-interference.
However, the foregoing self-interference signal that enters the receive channel is not merely a signal obtained after simple amplitude attenuation and phase change are performed on the transmit signal. Therefore, self-interference cancellation cannot be effectively performed by using the prior art, resulting in a receive signal with relatively poor quality.